Assessing Suitability of Various Morphological and Ionic Traits as Proxies for Barley Tolerance to Combined Salinity and Waterlogging Stress

ABSTRACT Waterlogging and salinity stresses significantly affect crop productivity and often coincide in nature. While adaptive responses to each of the individual stresses have been studied in detail, the traits conferring tolerance to combined stresses (and thus the most appropriate targets for breeding) remain poorly understood. In the present work, we studied the morphological and ionic responses of 11 barley varieties contrasting in salinity (NaCl) stress tolerance under waterlogging (WL) and combined waterlogging and salinity (WL + NaCl) stresses. Stress damage responses were much higher in plants under combined WL + NaCl stress than those under either stress alone. The adverse effect of combined stress was much greater in salt‐sensitive varieties than in more tolerant varieties. As shown by PCA analysis, growth traits such as shoot and root biomass, number and length of adventitious roots, and K + concentration contributed strongly to PC1. Under NaCl stress, PC1 (47%) and PC2 (24.2%) accounted for 71.2% of the variance, with growth‐related traits strongly correlated with PC1, while Na + concentration and salt damage index contributed positively to PC2. A significant negative correlation ( r = −0.86 and −0.96, respectively) was found between aerenchyma score and salt damage index under WL and combined stress, respectively. Overall, PCA, membership function value analysis, and correlation matrix analysis consistently identified the number of adventitious roots, percentage formation of aerenchyma, and shoot K + content as the traits most strongly associated with the stress damage index, highlighting their suitability as key phenotyping proxies for selection in breeding programmes.